The development of non-volatile memory devices with a 3-dimensional memory array is progressing. For example, there are memory devices having word lines stacked on an underlying layer, and semiconductor pillars that pierce therethrough. Memory cells and selection gates are disposed on the side face of the semiconductor pillars. Also, the gap between the semiconductor pillars is tending to become narrower due to size reduction in the memory array associated with the increasing of storage capacity. Therefore, manufacturing processes such as photolithography are becoming more difficult, and then, production yield may be reduced.